This invention relates generally to the art of alloys, and more particularly to the art of welding alloys.
Conditions of very high mechanical restraint can be encountered in welding, for instance, when depositing the root bead of a single-vee weld of pipes. Another condition where high mechanical restraint can occur is when making deep, localized repair welds. These conditions promote cracking in weld deposits especially for filler metals that have high strength and low ductility. Conditions of high mechanical restraint can be encountered when making either structural or repair welds of nickel aluminides. Cracking of such weld deposits is observed and it can be difficult or impossible to control with the normal filler metals used for nickel aluminide alloys. Cracking problems under high mechanical restraint conditions are overcome with the use of the high ductility filler metals that are the subject of this invention disclosure.
The two filler metals being used to weld nickel aluminide alloys are designated IC221W, U.S. Pat. No. 5,413,876, and IC221LA U.S. Pat. No. 5,725,693. The nominal composition of the IC221W alloy is Ni-8A1-7.7 Cr-1.5 Mo-3.1 Zr-0.003B wt %. The Ni-8A1-7.7 Cr wt % base composition of IC221W is identical to that of the base metal cast nickel aluminide alloys, i.e. IC221M and IC396M. IC221W is more resistant to solidification cracking than the base metal alloys and this is a critical property for obtaining crack-free welds with ICC221W filler metal. Because IC221W shares the same base composition with the base metal alloys it also closely matches their properties of high strength and relatively low ductility.
The nominal composition of the IC221LA alloy is Ni-16 Cr-4.5-Al 1.2 Mo-1.5 Zr-0.003B wt %. The chemical composition of this alloy was formulated to match those of the base alloys, but the chromium level was increased and the aluminum level was decreased to improve its ductility. The improved ductility properties of IC221LA make it the filler metal alloy of choice for most welding applications.
The cast nickel aluminide alloys could not be welded before the developments of the IC221W and IC221LA filler metal alloys. However, a need still exists for filler metal alloys that are chemically compatible with the base metal alloys and which have even higher ductility than that of the IC221LA filler metal alloy and for welding alloys that can withstand conditions of high restraint.
It is thus an object of this invention to provide a novel alloy.
It is a further object of this invention to provide a novel welding alloy.
It is a yet further and more particular object of this invention to provide a welding alloy for nickel aluminide alloys and to form a composite thereof.
These as well as other objects are accomplished by a substantially titanium and niobium free alloy comprising nickel and zirconium.